Dual circuit signal control



Dec. 2,1958 H. T. CHAPEK ETAL DUAL CIRCUIT SIGNAL CONTROL Fild Dec.

United States Patent i 2,862,662 .DUAL CIRCUIT SIGNAL CONTROL Henry T.Chapek and Heard S. Lowry, Jr., Manchester, Tenn., assignors to theUnited States of America as represented by the Secretary of the AirForce Application December 1, 1955, Serial No. 550,508 4 Claims. (Cl.235-92) This invention relates to computing, and particularly tocomputing circuitry utilizing successions of computing elements, eachincluding signal read-out and indicating facilities. f

A feature of the invention is the provision of novel resettingfacilities permitting interruption of the normal trend of signaltransfer (e. g. digital computing) at any stage of a complete cycle, bymeans operating to modify the potential characteristics of the signaltransfer elements themselves.

The invention is illustrated as incorporated in signal transfer elementsof the Eccles-Jordan type trigger amplifier. The action of this two-tubecircuit depends upon the fact that current flows through only one tubeat a time. This form of multivibrator employs direct coupling betweentheanodes and grids of the two tubes. It is a circuit'possessing twoconditions of stable equilibrium. One condition is when tube 1 isconducting and tube 2 is cut-oft; the other when tube 2 is conductingand tubel is cut-off. The circuit remains in one or the other of thesetwo conditions, until some action occurs which causes the nonconductingtube to conduct. The tubes then reverse their functions and remain inthe new condition as long as no plate current flows in the cut-off tube.Because of this sudden reversal or flopping from one state ofequilibrium to the other, this type of circuit is referred to as aflip-flop circuit.

The flip-flop circuits are arranged serially to form a counting oranalogous signal transfer system. Means are provided so that the sametube in each of the flip-flop circuits always conducts in the nullposition. One method is to drive the desired tube to the conductingstate in preparation for counting. The counting circuit then receivesinformation in the form of repeated pulses, the number of repetitionsimparting the desired information. These pulses actuate some or all ofthe flip-flop circuits which are arranged serially. It would bedesirable to have some visual indication of the state of each of theflip-flop circuits in the counting system and simultaneously acompletely independent output to any external device.

After a train of pulses into the counter, the visual indication for eachof the flip-flop circuits will then show whether or not they are in anull condition. If not, means are provided to reset the flip-flopcircuits to the null condition in preparation for another countingcycle.

One object of the invention is to provide a visual indication of thestate of the flip-flop.

Another utilization is to provide a simultaneous contact .output fromthe flip-flop circuit which is completely independent and which does notrequire the addition of cathode followers or relay pullers. Anotherobject of this invention is to provide a means for resetting theflip-flop circuits simultaneously effective upon all units of thecomputing chain.

Still further objects and advantages of the invention will be apparentin the following description and claims conice Patented Dec. 2, 1958 zsidered with the accompanying drawing showing a schematic Wiring diagramembodying the invention.

Referringto the drawing, Fig. 1, there are shown successive computingelements connected serially. Each one of the elements are identical andeach element is a modified type Eccles-Jordan flip-flop circuit. Thisflipflop circuit is comprised of two triode vacuum tubes 2 and 3. Eachof the triodes 2 and-3 are adapted to receive an actuating input pulsefrom common input terminal 39. This. input pulse is impressed upon thegrid 4 of tube 2 through capacitor 6 and upon the grid 5 of tube 3through capacitor 7. Each tube is provided with a grid resistor toground, 8 for tube 2 and 9 for tube 3. The cathode of tube 2 is providedwith resistor 14 to ground. Cathode 13 of tube 3 is provided withdivided resistors comprising resistor 14 and resistor 13 which isnormally shunted by switch 17. Cathode resistor 14 is common to tubes 2and 3. Cathode resistor 14 is by-passed to ground by capacitor 16.Resistor 18 in shunt with capacitor 20' couples the anode 10 of tube 2to grid 5 of'tube 3. Resistor 19 in shunt with capacitor 21 couples theanode of tube 3 to grid 4 of tube 2. The anode of tube 2 is loaded by aseries connected resistor which is divided into resistors 22 and 26. Theoutput of the flip-flop circuit 1 is taken from point 28 betweenresistors 22 and 26. This output is adapted to feed the next succeedingflip-flop circuit. Anode 11 of tube 3 is loaded by series connectedresistor 23 and inductance 25. Inductance 25, an energizing coil ofrelay 40, is shunted by diode 27. Single pole-double throw switch'29 isactuated by inductance 25. There are two voltage sources 34 at volts and33 .at +25 volts. Connected in series between 33 and 34 are resistors31, 32 and oneside 36 of switch 29. In shunt with resistor 32 andvoltagesource 33 is neon tube 30, vThe other side 37 of switch 29 is theoutput line 38 to output connection 35.

With the flip-flop circuit in the null position (i. e. at rest) tube 2is conducting and tube 3' is nonconducting. Relay 40 is not energized sothat single throw-double pole switch 29 connects resistors 31 and 32 topoint 36 and then across voltage sources 33 and 34 thus forming avoltage dividing network. Neon tube 30 is in shunt with only a part ofthis voltage dividing network and receives an inadequate voltage toionize it. With tube 2 conducting and tube 3 nonconducting, one methodto actuate the flip-flop circuit is to apply a negative pulse to thecommon input 39. This will decrease the grid potential of tube 2. Theplate potential of tube 2 rises sharply, carrying with .it the gridpotential of tube 3, thus allowing tube 3 to conduct. The accompanyingdecrease in plate potential of tube 3 forces the grid potential of tube2 below cut-off. Tube 3 remains in a conducting state and tube 2 remainsin a nonconducting state.

When tube 3 is in a conducting state and tube 2 is nonconducting, relay40 is energized by reason of the current flow through inductance 25.Diode 27 damps the transients through inductance 25. The series resistor23 isolates the capacity to ground of inductance 25, thus preventingthis capacity to ground from effecting the action of the flip-flop.Resistor 23 also allows compensation for different ohmic values of relayinductance.

The inductance 25 being in an energized state, single pole-double throwswitch 29 is actuated and switch 29 is shifted from contact 36 to 37.Neon tube 30 is now connected in series with resistor 32 and both areacross voltage sources 33 and 34. There is adequate voltage to ionizeneon tube 30 which glows. This serves as a visual indication of thestate of the flip-flop. Simultaneously line 38 provides a contact outputdirectly to terminal 35. This may also serve as a convenient means forreading out the state of the counter without disturbing the count.

At any stage of a counting cycle or at its completion, it maybedesirable or necessary to re-set the flip-flop in the computing chain toa null or rest condition, therebyrequiring all of tubes 2 to revert to aconducting condition'and tubes 3 to a 'nonconducting one. A resettingpulse is provided from source 55. This willjenergize seriesconnectedrelays '41 to 54; The. description of operation. in-flip-fiop 1 isrepresentative of all. Switch 17 shunting resistor 15 will openand'theteby'will'provide tube 3 with divided cathode resistors 14 and15.Where tube 3 is in a conducting state thebias on tube 3 will increase ina negative direction. The plate potential of tube 3 rises, :carryingwith it the grid potential of tube 2 thus allowing tube 2 .to conduct.The accompanying decreaseJin plate potential y-of'tube 2 forces the gridpotential of tube 3 below cut-off. Tube 2 remains in a conducting stateand tube 3 remains in .a nonconduct-ing state. Switch 17 again shuntsresistor 15. Flip=flop 1 is'now in a standby condition availableforanother counting cycle.

What is claimed is:

1. A computing system comprising a successionof twostate devices each ofwhich devices includes a pair of anode circuits, a pair of cathodecircuits, and-a pair of excitation grid circuits, means for transferringsignals from each of said two-state devices to the next succeeding twostate device, relay-operated switch means in each of said cathodecircuits, and means controlled by said switch means for modifying thepotential characteristics of the signal transfer means and therebycontrolling the signal transferring operations; I

2. A computing system as defined in claim 1, wherein the means formodifying the potential characteristics of the signal transfer meanscomprises a bridging circuit coupling the cathode circuits of each ofthe said-twostate devices, said bridging circuit being of predeterminedresistance value, and wherein said relay-operated'switch meansestablishes a conductive path shunting said'bridging circuit, 7

3. A computing system comprising a succession of twostate devices eachof which is comprised of two tubes of the triode type employingcross-coupling between the plates and grids of the said tubes, switchoperating relay means in the plate circuits of one tube of each of thesaid two-state devices, means responsive to the operation of each of thesaid two-state devices to energize said relay means and thereby controlthe signal output from each of the said two-state devices and includinga neon tube type indicating element, and a voltage dividing network incircuit with said neon tube, said relay, switch and network cooperatingto provide a direct output from said two-state device.

4. A computing system comprising a succession of two state devices eachof which is comprised of two tubes of the triode type employingcross-coupling between the plates and grids of the said tubes, switchoperating relay means in the plate circuits of one tube of each of thesaid two-state devices, means responsive to the'operation of each of thesaid two-state devices to energize said relay means and thereby controlthe signal output from each of the said two-state devicesand including aneon tube type indicating element, and a voltage dividing network incircuit with said neon tube, said relay, switch and net work cooperatingto provide a direct'output from the said two-state device,simultaneously with the flashing of said neon tube.

References Cited in the file-of this patent UNITED STATES PATENTS2,168,198 Frink Aug. 1, 1939 2,428,126 Nickolson Sept. 30, 19472,521,788 Grosdofi Sept. 12, 1950 2,620,400 Snijders Dec. 2, 19522,630,969. Schmidt Mar. 10, 1953 2,756,934 Zifier July 31, 1956

